People with ADHD commit more crimes while off medication, study says

Ritalin is one of several medications used to treat ADHD. A new study finds… (Joe Raedle / Getty Images )

People diagnosed with attention deficit hyperactivity disorder are more likely to commit crimes when they are not receiving medication, according to a study published Wednesday in the New England Journal of Medicine.

Numerous studies have shown that ADHD is associated with an increase in criminal behavior, but it has remained unclear how medication use influences this equation after adolescence.

The study, which followed 25,656 Swedish people diagnosed with ADHD from 2006 to 2009, is the largest such analysis of the long-term effects of ADHD treatment. The researchers, led by Paul Lichtenstein of the Karolinska Institutet in Stockholm, compared periods in which their subjects were on medication with periods in which they were not. By doing so, they were able to do many comparisons of the same subjects at different points in time, reducing the possibility that confounding factors -- such as socioeconomic status -- would cloud any associations they uncovered (they used statistical methods to control for such factors as well).

A decent number of the subjects committed crimes at some point during the study: 36.6% of men were convicted of a crime, and 15.4% of women.

And when the researchers looked to see whether medication use was associated with a drop in crime, the results were unequivocal: Among men, there was a 32% drop in crime while the subjects were on their meds. That number was 42% among women.

The authors point out that associations between two behaviors, such as medication use and criminality, can be easily confounded. What if, for example, a criminal conviction led to a reduction in medication adherence instead of the other way around? But when the researchers looked to see whether that was the case, they found that the association held regardless of the order. They tested for many other confounds as well, including the use of other drugs, and the association remained.

Nevertheless, the authors do not suggest that everyone with ADHD should be on meds. Instead, they suggest the potential behavioral benefits, even in adulthood, should "be carefully weighed against potential adverse effects of medication, including overprescription and side effects."